Apple found 106 different ongoing cases of underage workers in its suppliers in China and 70 historical cases, according to its seventh annual supplier audit.

The fruity firm said it was "dismayed to discover" that one supplier, Guangdong Real Faith Pingzhou Electronics (PZ), was rampantly violating the policy, with 74 different cases of workers under 16.

The annual audit started up as the company has attracted more and more criticism for exploiting cheap Chinese labour to build its high-priced iDevices. In particular, reports of a spate of suicides at now-famous Apple supplier Foxconn drew a lot of attention to the insanely long hours workers were often forced to do before crawling into the cramped living spaces they were allocated at the factory sites.

Apple said it has now stopped all business with PZ and informed local government about a large labour agency, Shenzhen Quanshun Human Resources Company, which it alleged had been knowingly providing the children to PZ, even helping families to forge false age verification documents.

"The agency had its business licence suspended and was fined," the company said in the report. "The children were returned to their families and PZ was required to pay expenses to facilitate their successful return."

In total, 11 factories supplying parts for iDevices were found to have employed underage workers, but in the other cases, the facilities apparently "had insufficient controls" to check their staff's age, and there was no intentional hiring of kids, Apple said.

Apple said it was making good progress reducing working hours per week, and said that 92 per cent of its suppliers were compliant with a maximum 60-hour week with at least one day off and only voluntary overtime.

The audit found that 34 factories required female workers to be screened to see if they were pregnant before they were hired and 25 were doing other medical testing like Hepatitis B tests.

Apple also discovered eight facilities with "bonded labour", where foreign contract workers are forced to pay "fees" for getting the job that are so prohibitive they end up making almost no money in the first months or even year or so of their employment. Apple said that said in the report that it had asked those suppliers to reimburse the workers for any fees that totaled more than one month's net wages. Those payments ultimately amounted to $6.4m. ®